In recent years, techniques for suppressing penetration of fluid, such as water, or solids, such as dust, into inside of an in-wheel motor mounted to a vehicle have been suggested.
For example, an in-wheel motor described in Patent Document 1 is configured as follows. That is, an inner case of a hollow shape is supported by a vehicle through a suspension device. A stator is fitted to an outer periphery of the inner case. A cylindrical outer case is fixed to a rotatably supported hub and is positioned on the outer periphery of the inner case. A permanent magnet is fitted to an inner periphery of the outer case through a gap so as to be opposed to the stator to constitute a rotor. The outer peripheries of the stator and the rotor are covered by an inner case cover and an outer case cover, respectively. A labyrinth structure is formed by the inner case and the outer case on a portion communicating with a gap between the rotor and the stator.